1. Field of the Invention
The present invention relates to pipe couplings, and particularly to pipe repair couplings.
2. Description of the Prior Art
The mending of broken pipe, particularly underground pipe, has traditionally been a laborious and complicated procedure. For the repair of broken PVC (polyvinyl chloride) pipe, this procedure has traditionally comprised isolating the break and then excavating around or otherwise clearing a long section of the PVC pipe surrounding the break. A long section of pipe on both sides of the break is required because the standard repair coupling until now has comprised a short piece of similar PVC piping which is radially enlarged relative to the pipe to be repaired and which is slipped and solvent welded over the broken ends of pipe. This requires that the broken ends of pipe be relatively free in order to have enough play to be bent back so that the weld coupling may be inserted and then the broken ends of pipe cammed toward each other into the weld coupling. This method of bending and camming the pipe sections to be joined frequently results in an insertion of extra pipe length into the existing pipe line exerting additional flexural stresses upon the pipe line. This problem is exacerbated in the instance of PVC pipe having a large diameter since in order to gain the required flexibility, a much greater length of pipe must be cleared on either side of the break. The same difficulties pertain wherein an additional branch pipe is to be added to an existed line since the existing pipe must be cut and a T-coupling inserted in the manner described above.
In repairing non-PVC pipe, the process is much more complicated. Frequently the entire length of pipe which is broken must be removed and a new length of pipe, if it is compatible, must be replaced and sometimes forced into place to fit the existing threaded couplings. Otherwise, a torch cutting procedure must be employed and then a new length of pipe must be fitted and welded or otherwise heat fused into place.
In both of these instances, a collapsible repair coupling would be useful since only a small area of the pipe surrounding the break need be removed, the collapsible repair coupling fitted into place and then expanded to fit the free ends of pipe. The only pipe coupling device incorporating a collapsible configuration of which the applicant is aware is a PVC device which is solvent welded onto a PVC line and which has a lubricated extendable housing having a threaded attachment whereby the housing may be rotated in order to fit a water or other fluid source. The lubrication which allows for the expansion and compression of the device is exposed to environmental corruption and frequently sticks. This device is unsuitable for PVC repair work since corruption of the lubricated seal may foul the device and consequently the device must be protected by an outer plastic sheath or other cover.
Applicant is aware of no collapsible repair coupling or other collapsible coupling having entirely internal and nonfoulable means of extension.